Improved photolithographic technologies based on short wavelength radiation (e.g., as generated by an ArF excimer laser operating at 193 nm), or other such short wavelength sources, are useful in the pursuit of ever faster and more efficient semiconductor devices by increasing device density of an integrated circuit. Photoresist materials useful in such short wavelength applications include chemical amplification-type radiation-sensitive resin compositions, which rely on the efficient interaction of a resin component having an acid labile functional group, and a photoacid generator that generates an acid upon irradiation.
The requisite properties for photoresist materials useful for ArF excimer laser lithographies include transparency (i.e., low optical density) at 193 nm, as well as high etch resistance, conveyed by high carbon density and polycyclic ring structures. Useful photoresist platform resins include those based on a poly(meth)acrylate-based backbone and a carboxylic acid moiety protected with a bulky tertiary alkyl group, which is highly transparent at 193 nm. The efficiency of deprotecting (also referred to herein as “deblocking”) the carboxylic acid directly correlates with the contrast and resolution.
A variety of different (meth)acrylate based monomers, having tertiary ester groups which are sensitive to acid, are known. For example, U.S. Patent Application Publication No. 2007/0275324 A1 discloses (meth)acrylate esters based on cycloalkyl moieties having a tertiary center in which the ester oxygen attaches to a tertiary alkyl ring carbon atom having another alkyl or cycloalkyl substituent at the same center (i.e., to make a quaternary center). Polymers prepared using these monomers can provide contrast in a photoresist.
However, as the critical dimension (CD) of semiconductor devices shrinks, still higher resolution photoresists which provide narrow CD control are required for manufacturing of devices at or below the 45 nm device design node.